I. Field of the Invention
This invention relates generally to improved catheter apparatus for facilitating the recanalization of a stenosed coronary artery and more particularly to an improved guide catheter system whereby a guide catheter member can be advanced beyond the coronary ostium and into the coronary artery itself up to the point of the stenosis.
II. Discussion of the Prior Art
In treating coronary artery disease, a variety of surgical techniques are employed to recanalize an occluded or partially occluded artery segment without requiring open heart surgery. Using the technique pioneered by A. Gruntzig, a catheter having an expander (balloon) at its distal end is routed through the vascular system and ultimately into the coronary artery with the balloon being juxtaposed with the stenotic lesion. Once so positioned, the balloon is inflated to compress the plaque into the wall of the blood vessel, thus restoring patency.
In another procedure, referred to as an atherectomy, a catheter having a rotatable cutter at its distal tip is advanced through the vascular system and when the tip is made to abut the atheroma, a motor at the proximal end of the catheter is used to drive the cutter to surgically "tunnel" through the lesion. In this regard, reference is made to the Rydell U.S. Pat. No. 4,784,636, assigned to applicant's assignee.
Still others have incorporated a fiber optic bundle in a catheter and a laser is used to burn through the plaque comprising the arterial blockage. In this regard, reference is made to the Moore et al U. S. Pat. No. 4,669,465, assigned to GV Medical, Inc., of Minneapolis, Minn.
The foregoing are exemplary of working catheters, i.e., the catheters that are directly involved in the recanalization through expansion, excision or ablation. To properly position the working catheter, it is also necessary that a guide catheter be utilized. A guide catheter of the prior art typically comprises an elongated, flexible tube having an internal lumen sufficiently large to receive and pass the working catheter therethrough. In that the catheters are generally introduced into the femoral artery and then advanced through the vascular system to the heart, the guide catheter must possess a characteristic of "torqueability" meaning that it can transmit a twisting force applied at its proximal end to the distal end to facilitate the ability to steer it through the appropriate vascular branches. The torqueability characteristic is achieved by the appropriate choice of materials for the guide catheter shaft or by incorporating a braided sheath of wire strands embedded in the wall of the guide catheter. Those wishing further information concerning the construction of a typical prior art guide catheter are referred to the Stevens U.S. Pat. No. 3,485,234, assigned to the Cordis Corporation of Miami, Fla.
When it is considered that the lumen of the guide catheter must be large enough to pass the working catheter and that the guide catheter shaft must exhibit acceptable torqueability and stiffness characteristics, it tends to dictate a guide catheter having a relatively large outside diameter. In fact, it has not been possible in the past to advance the distal end of the conventional guide catheter beyond the coronary ostium. Where the site of the lesion in the coronary artery is several centimeters beyond the ostium and it becomes necessary during the recanalization procedure to exchange working catheters, damage may be done to the delicate tissue of the intima.